In an electromagnetic device, such as an electromagnetic actuator of an electronic valve timing system for a motor vehicle, it is often necessary to join a "soft" magnetic material and a hardened, non-magnetic or magnetic material. Typically, the soft magnetic material is in the form of an armature and is annealed to remove most internal stresses and any carbon which may be within the material. The annealing process accounts for consistent magnetic and mechanical performance characteristics of the magnetic circuit components. In an actuator, the hardened material is in the form of a shaft.
One approach to joining the shaft to the armature is to physically deform the armature to engage a feature in the shaft. However, this approach may involve significant tooling costs in order to perform the deforming operation. Further, a deforming operation is not a batch type process and thus, it may take a significant amount of time to join a plurality of shafts and armatures, since generally only one shaft-armature connection can be done at a time.
Accordingly, there is a need to join a soft magnetic material to a hardened material with low tooling costs and in a batch-type process.